High-resolution carbon isotope stratigraphy and mammalian faunal change at the Paleocene-Eocene boundary in the Honeycombs area of the southern Bighorn Basin, Wyoming

Abstract

The Paleocene-Eocene boundary is defined chemostratigraphically by the onset of a 100 kyr global carbon isotope excursion (CIE) that is recognized in marine and continental strata in both carbonate and dispersed organic carbon. The CIE is important in continental sections as a proxy for environmental change during the Paleocene-Eocene thermal maximum (PETM), which clearly affected faunal succession in Paleocene-Eocene mammals. At Polecat Bench in the northern Bighorn Basin, Wyoming, the CIE is in the Willwood Formation, where it spans four mammalian biozones from part of latest Clarkforkian Cf-3, through early Wasatchian Wa-M (Meniscotherium), Wa-0, and part of Wa-1. Here we report a new high-resolution study of the CIE recorded in dispersed organic carbon of the basal Willwood Formation in the Honeycombs area of the southern Bighorn Basin.